Mechanical ventilation (MV) is used clinically to maintain gas exchange in patients that require assistance in maintaining adequate alveolar ventilation. Common indications for MV include respiratory failure, heart failure, surgery, etc. Although MV can be a life-saving intervention for patients suffering from respiratory failure, prolonged MV can promote diaphragmatic atrophy and contractile dysfunction, which is referred to as ventilator-induced diaphragm dysfunction (VIDD). Extended time on the ventilator may result in VIDD and thereby increase health care costs and greatly increase patient morbidity and mortality. Research reveals that 18-24 h on MV is sufficient to develop VIDD in both laboratory animals and humans.
2.1 million patients are ventilated in United States each year representing 36% of the ICU population. The estimated annual cost to manage ventilated patients in the US each year is 27 billion representing 12% of all hospital costs. It has been found that approximately 60% of the ICU patient population intubated are scheduled for extubation and weaning. Unfortunately, nearly 45% of patients receiving invasive ventilation therapy in the ICU have difficulty weaning and develop some form of dependency on the ventilator. This often leads to the need to extend the patients ICU/CCU stay beyond what is typically required for the original medical condition since many encounter prolonged weaning periods. The projected number of patients requiring prolonged acute mechanical ventilation on an annual basis in the US is expected to grow to be greater than 600,000 patients by the year 2020 with the overall cost of managing these patients exceeding $64 billion.
Animal models have shown that maintaining some level of stimulation to keep the diaphragm working when on a ventilator is enough to prevent or reduce atrophy. Unfortunately having a patient breath spontaneously or in assist mode from the initiation of ventilation is not always possible due to the level of sedation and/or disease state.
In these cases, phrenic nerve pacing is a viable alternative to control the level of effort exerted by the patient and also in cases where the patient has become ventilator dependent and requires a training regime of pacing to strengthen their muscles. Phrenic nerve pacing in animals has also been shown to prevent diaphragm atrophy. Pacing the phrenic nerve in patients who suffer from spine injury who have lost the ability to breath, has be shown to reverse the effect of atrophy over a 6 months training period where the diaphragm has not been used in years. It is generally better to prevent a disease condition rather than remediate it. Initiating stimulation early in the regime of ventilation will most likely have the most profound effect on reducing time to extubation.
Methods currently exist to electrically stimulate the phrenic nerve in chronically ventilated patients as an alternative to mechanical positive pressure ventilation, to avoid some of the potential side effects of long term ventilation already mentioned. More recently central sleep apnea events have been reduced with the use of implanted phrenic nerve pacing at the onset of apnea. Phrenic nerve pacing has also been achieved with the use of trans venous electrical stimulation. Patients who have permanent respiratory insufficiency due to absence or reduction in a central respiratory drive descending from the brain stem (C3, C4 and C5) are now using commercially available pacing products to pace the diaphragm muscle by electrically stimulating the phrenic nerves using implanted electrodes. These implanted stimulation devices use some form of phrenic nerve cuffs, or diaphragm electrodes all of which require invasive surgeries. The feasibility of such techniques to prevent diaphragm atrophy or wean patients from a ventilator are limited by the cost and risks associated with permanently implanted phrenic nerve pacing electrodes and are not a viable alternative for VIDD patients.
Diaphragm muscle pacing, phrenic nerve pacing, and combined intercostal and unilateral diaphragm pacing techniques are currently being used to wean patients without respiratory drive from ventilators in the chronic setting of ventilation and reduce the incidence of infection, atelectasis, and respiratory failure. There exists the need for a short term pacing alternative which can be easily connected to a patient in the ICU or post-surgery or similar setting to wean or prevent VIDD from occurring.
Embodiments described herein seek to meet this need by providing a diaphragmatic stimulation system which includes an electrical lead(s) component that is readily employed without the need of a permanent or surgical implantation. The system measures the level of effort in the patient's breathing. The level of stimulation is titrated with that level of effort measurement. Taken together these embodiments provide a less invasive system that can accommodate modest patient motion and function well within the context of a surgical or ICU recovery setting.
Embodiments of the present disclosure provide a system and methods of its use which when properly utilized, reduce the occurrence of VIDD by providing stimulation to the diaphragm of a patient undergoing MV and thereby provide improved patient outcomes if/when transitioning from MV and provide reduced healthcare costs.